This invention relates to the treatment of minerals and, more particularly but not exclusively, is concerned with the treatment of clay minerals.
A conventional way of improving the smoothness, printability and whiteness of paper is to apply to the surface of the paper a coating composition, which comprises an aqueous suspension of a white pigment, conveniently a kaolinitic clay, an adhesive and water. In order that the coating composition may be smoothed on to the paper it must be capable of flowing at least to a limited extent but, since any water in the composition must be removed by thermal drying, it is advantageous that the water content of the composition should be as low as possible.
Is is an object of this invention to provide inter alia a clay mineral which has desirable properties when used as a pigment in a paper coating composition; a process for treating an aqueous suspension of a clay mineral so as to improve the rheological properties of the clay mineral in aqueous suspension; and a process for treating an aqueous suspension of a clay mineral so that the clay mineral forms a cake of high permeability to water during a filtration operation so that the rate at which the aqueous suspension may be dewatered by filtration is increased.